Fibrous adsorbents have been widely used for recovering metals from aqueous systems, such as seawater, fresh water, wastewater, drinking water, ultrapure water, and other less common types of waters, such as hot spring water and water rich in precious metals. Many of the fibrous adsorbents used for the extraction of metals have a polymeric backbone (trunk) with functionalized polymeric grafts extending substantially perpendicular to the backbone, wherein the functional groups in the polymeric grafts contain metal-binding groups.
In the conventional art, polymer fiber adsorbents are typically prepared via radiation-induced graft polymerization (RIGP) because RIGP maintains strong yet ductile properties of trunk polymers, such as polyethylene, and adds specific chelate-forming graft chains containing functional groups for the recovery of metals. However, RIGP also has many limitations, including the high cost of operation when an electron-beam irradiation is used, a limited choice of monomers tolerable to irradiation, the lack of control over polymer structures (e.g., graft chain composition, composition distribution, and degree of grafting), and in some cases, the formation of homopolymers. The lack of control in the grafting process often results in fibers with degraded adsorption or selectivity performance. Thus, there would be a significant benefit in a process that could produce metal-binding fibers with greater adsorption or selectivity performance. There would be a further benefit in such a process that is less costly and which may also be more amenable to control and fine tuning of the metal-binding characteristics of the fiber.